This invention relates generally to apparatus for guiding and cooling a heated image-carrying support moved along a path. More particularly, this invention relates to apparatus for guiding and cooling a copy sheet carrying a fused toner image as it exits from a heated fuser.
Typically, in the electrographic process, an original is illuminated by a light source to form an image which is projected upon a photoconductive member to produce a latent electrostatic image corresponding to the original. The latent electrostatic image is developed by means of fusible particles to produce a visible toner image which is transferred to a support such as a copy sheet of plain paper. The unfused toner image may be fixed to the support by means of heat and pressure by passing a copy sheet carrying an unfused toner image through the nip of a pair of rollers, at least one of which is heated. A fused copy sheet exiting from the roller nip has been heated by the heated roller and its toner image is in a tacky state. The copy sheet also has a tendency of curling due to the drying out of the sheet during fusing and due to the curvature of the fusing nip. Thus, it is desirable to cool the copy sheet after it exits from the fuser in order to minimize curling and to prevent copy sheets from sticking together in an output tray. Cooling the copy sheet also prevents image smear and thermal hazard and messiness to an operator handling a hot copy sheet having a tacky toner image.
Various proposals have been made to handle and cool copy sheets as they exit from a fuser. For example, in U.S. Pat. No. 4,003,568, issued Jan. 18, 1977, for "Fluid Conveyer," by K. K. Stange et al, there is disclosed apparatus for transporting and cooling toner bearing sheets discharged from a fuser. The apparatus is provided with a pair of passageways in which an air flow is created (1) by means of a vacuum located at one end of the passageways and (2) of a source of pressurized air to direct the copy sheets out of the passageways in a direction transverse to the entering direction. Commonly assigned U.S. Pat. No. 3,914,097, issued Oct. 21, 1975, for "Sheet Guide and Cooling Apparatus," by D. R. Wurl, discloses apparatus having a thermally conductive surface located at the exit of a fuser for guiding and cooling sheets bearing a developed image exiting from the fuser. Vacuum means are associated with the surface to draw a copy sheet into contact with the surface and to provide a flow of cooling air to cool the surface. Research Disclosure No. 18445, dated August 1979, page 430, for "Post-Fuser Copy Sheet Transport," discloses a post-fuser transport that prevents curl in copy sheets exiting from a heated roller fuser by means of upper and lower air plenums which supply a flow of air along the copy sheet path to cool the copy sheet as it is transported through a tunnel formed by the plenums.
Although the techniques for guiding and cooling a copy sheet exiting from a fuser disclosed in the above disclosures may have been suitable for the purposes for which they were intended, in each of these disclosures, there is only one fluid flow for both cooling and guiding the copy sheet. The single fluid flow functions to draw a copy sheet into contact with a guide member which cools the copy sheet and also to cool the guide member.